(Not applicable.)
The present invention relates to an ultraviolet imager system or method, useful inter alia, for the detection of fingerprints and other forensic evidence at crime scenes, on evidentiary objects or materials, or elsewhere. The invention provides a novel system for detecting images by ultraviolet light (xe2x80x9cUVxe2x80x9d hereinafter) and capturing the images on film or electronic media. More particularly, the present invention provides a novel ultraviolet light-imager system that permits simultaneous photographing and viewing of fingerprints and other evidence.
Special tools are frequently used by law enforcement personnel when evaluating a crime scene to collect forensic evidence that is invisible to the human eye. Examples of such evidence include bodily fluids, fingerprints on porous and non-porous surfaces, forged documents, explosives residue and trace evidence e.g., hair, fibers, etc. One commonly used tool is a forensic light source that provides fluorescent light to detect and record forensic evidence.
A recently introduced complementary tool to the forensic light source is a tool that relies on intensified short-wave ultraviolet reflectance as opposed to ultraviolet-induced fluorescence. Such an ultraviolet light tool can reveal additional evidence on non-porous surfaces where other forensic light sources are not useable or the subject requires processing with powders or fluorescent dyes.
Conventional forensic tools that utilize ultraviolet light reflectance from an ultraviolet light source, enable a traditional photograph to be taken at the output of an intensifier tube. However, the resolution of such photographs is poor, being limited by the resolution of the intensifier in line pairs/mm.
One ultraviolet light tool that does not rely on the output of an intensifier to obtain a photograph is a xe2x80x9cSCENESCOPExe2x80x9d (trademark) ultraviolet imager, available from applicant""s assignee, Jobin Yvon, Inc., which is a system that employs a modified single lens reflex camera, notably, a Nikon (trademark, Nikon Corp.) FM2 camera The xe2x80x9cSCENESCOPExe2x80x9d (trademark) imager utilizes an intensifier coupled to the viewing output of a modified 35 mm camera to provide both non-intensified photography of ultraviolet light reflectance from fingerprints on various backgrounds, and simultaneous intensified image focusing and viewing.
The intensifier operates electronically to increase the luminescence of the image and provide a visible wavelength output for example on a video screen. The intensifier is used to help focus the camera when using an invisible light source such as ultraviolet light (200-400 nm) or infrared (above 700 nm). Direct focusing is not feasible since ultraviolet light or infrared images are not visible to, and may be harmful to, the naked eye. A problem with the xe2x80x9cSCENESCOPExe2x80x9d (trademark), is that an inferior quality image may be obtained at the intensifier which, pursuant to the present invention, can be attributed to the low intensity of the ultraviolet light image which is received by the intensifier.
There is accordingly a need for an improved ultraviolet light imager which can overcome this problem.
The present invention solves the problem of poor focus image quality in an ultraviolet imager of the type employing an intensifier coupled to the viewing output of a camera. To solve this problem, the invention provides an ultraviolet light imager comprising:
a) a camera having:
i) a focusable camera lens to input ultraviolet light images to the camera;
ii) a film holder for a light-sensitive film to capture images received from the camera lens, the spacing of the camera lens from the film being adjustable to focus an ultraviolet image on the film; and
iii) a camera mirror having an ultraviolet-reflective surface to reflect a portion of the image light received from the camera lens to provide a reflected ultraviolet image for use in focusing the camera lens;
and
b) an image intensifier optically coupled to the camera to receive the reflected ultraviolet image from the camera mirror and provide a viewable output; wherein the reflected ultraviolet image is focused to the viewable output of the intensifier.
Preferably, the camera lens includes a first ultraviolet coated mirror and a quartz or fused silica ultraviolet-transmissive camera lens. The ultraviolet-imager system can also include a second ultraviolet coated mirror coupled to the camera through a lens system, the image intensifier being optically coupled to the second ultraviolet reflectively coated mirror to receive images therefrom.